Elevator safety device



Feb. 27, 1934.. J. DUNLOP ELEVATOR SAFETY DEVICE.

Filed Nov. 26

INVENTOR ATTORNEY WITNESSES:

Patented Feb. 27, 1934 UNITED STATES PATENT OFFICE ELEVATOR SAFETY DEVICE corporation of Illinois Application November 26, 1930 Serial No. 498,389

15 Claims.

My invention relates to elevators and more specifically to elevator safety devices for stopping and holding the car under predetermined emergency conditions.

It is an object of my invention to provide an elevator safety device which, when actuated, will automatically prevent the rate of deceleration of the car from exceeding gravity or any predetermined limit desired.

It is also an object of my invention to provide a safety device which, when actuated, will apply a constant braking force to bring the car to a smooth stop, irrespective of the continued rotation of the safety drum.

It is a further object of my invention to provide a safety device wherein the motion of the car becomes efiective to complete the application of the device after the rail-engaging surfaces have initially engaged the rails, whereby the maximum allowable braking force will be applied promptly.

It is also an object of my invention to provide an elevator system wherein the safety device becomes efiective to retard the car when it runs beyond its terminal.

A further object of my invention is to provide an elevator system wherein a single safety device will be actuated to retard the car in response to overspeeding when approaching a terminal at an insufiiciently reduced rate of speed, and from overrunning a terminal, irrespective of the speed.

The invention itself, however, both as to its organization and its mode of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment, when read in conjunction with the accompanying drawing, in which:

Figure 1 is an elevational view partially representing an elevator system provided with a safety device in accordance with my invention;

Fig. 2 is an enlarged view partially in elevation and partially in section, as indicated by line II--II of Fig. 3, and showing the relative positions of the rail-gripping jaws and the guide rail and details of the system; and

Fig. 3 is an enlargedhorizontal sectional view of the safety device included in Fig. 1.

Referring to the drawing, the apparatus shown in Fig. 1 comprises an elevator car C supported by a hoist cable Ca which passes over the usual hoist sheave S to the counterweight Cwt. The hoist sheave S may be driven and controlled by any conventional hoist motor and elevator system (not shown).

The usual governor rope 11 passes over a governor sheave 12 above the hatchway, under an idler sheave 13 at the bottom of the hatchway, and carries a minnie ball 14 which is releasably received by the spring clip 15 on the car.

Associated with the sheave 12, and driven thereby, is a conventional speed-responsive device, such as a governor 16. A pair of rope-gripping jaws 17 and 18 are pivotally mounted on opposite sides of, and adjacent to, the governor rope where it passes from the sheave 12. The jaws are provided with concentric rope-gripping surfaces which will grip and hold the rope, if it is moving downward, when they are rotated into contact therewith. The rope-gripping jaws 17 and 18 are actuated from the governor 16 by a pivoted lever 19 and a connector 20 associated therewith.

Secured to the free end of the lever 19 is a rope 21 which passes over suitable guiding pulleys 22 and 23 and extends to the bottom of the hatchway where it is secured to a pivotally mounted cam 24. The cam 24 is pivotally mounted on a pair of link members 25 and 26 which are effective to project the cam outward into the hatchway, when it is raised by the rope 21 controlled by the overspeed governor 16, for a purpose to be subsequently set forth.

A safety cable 27 is attached to the governor rope 11 and passes around guide pulleys 28 and 29, thence around the drum 31 (see Fig. 3) of a safety device which is mounted under the elevator car C.

The safety device, as shown in Fig. 3, comprises two pairs of rail-gripping jaws 32 and 33 mounted in cooperative relation for gripping the guide rails 34 and 35. Conical or wedge shaped actuators 36 and 37 are mounted adjacent to the inner extremities of the rail-gripping jaws on shafts 38 and 39 rotatably and slidably supported on a plurality of cross members 40. The inner end of shaft 38 is threaded and extends through the end wall of the safety drum 31 which is provided with a cooperative threaded portion. The inner end of shaft 39 is attached to a piston 41 which is slidably received in a cylinder 42. The cylinder 42 is attached to one end of a shaft 43, the other end of which is threaded and extends through the adjacent end of the safety drum which is threaded to receive the same.

It is to be noted that one of the threaded shafts 38 and 43 is provided with a right-hand thread and the other is provided with a left-hand thread, whereby rotation of the drum 31 in one direction will force the shafts away from each other and rotation in the other direction will pull the shafts toward each other.

The space within the cylinder 42 between the piston 41 and the end wall attached to shaft 43 is filled with a suitable pressure-transmitting fluid, such as oil. Seated in the upper side wall of the cylinder is a spring pressed valve 44. The valve is normally seated by an adjustable compression spring 45. One end of a pivoted lever 46 is connected to the valve 44 and the other end carries a weight 47. By means of an adjustable screw 49, the tension of the spring 45 may be varied to adjust the pressure with which the valve is seated. A housing 48 may be, attached to the cylinder to enclose the weighted valve. It is to be understood that the valve 44 is mounted on top of the cylinder. In other words, in the view of the safety device shown in Fig. 3, the section through the valve 44, cylinder 42, valve housing 48 and drum 31 is cut by a vertical plane, and, through the remainder of the device, by a horizontal plane.

The outer extremities of the rail-gripping jaws are dovetailed to slidably receive separate railengaging shoes 51. That the rail-engaging shoes 51 are dovetailed into the ends of the jaws is clearly shown in Fig. 3. The shoes are of wedgelike formation, and inclined backing surfaces are provided by the jaws, as clearly shown in Fig. 2. A limiting stop member 52 may be welded or bolted across the top of each rail-engaging piece to limit the normal lowermost positions thereof when the jaws are disengaged from the rails. If

.,desired, a similar limiting stop member may be welded or bolted across the bottom of each railengaging piece to limit the relative upward movement thereof when the jaws are moved to railengaging position. Although I have shown the rail-engaging shoes mounted in direct slidable engagement with the jaws, it is to be understood that rollers or any other well known frictionreducing means may be provided therebetween if desired.

As shown in Fig. 2, the tapered rail-engaging shoes 51 may be moved to rail-engaging position without moving the rail-gripping jaws together. For this purpose, I provide an actuating lever 53 which is pivotally mounted on the car and may be provided with a roller 54 on one end. A

suitable rope or connecting member 55 is attached to the other end of the pivoted actuator lever 53 and extends thence to the tapered railengaging shoes 51. By extending the shaft which supports lever 53 to the opposite side of the car, a similar lever may be provided for actuating the adjacent rail-engaging shoes. The rope 55 is of such length and the lever 53 is so mounted that the free end projects out into the hatchway to support its roller 54 a predetermined distance from the car.

An adjustable spring 56 may be provided on the car for predetermining the normal position of the lever 53. The position of the lever 53 on the car, and the movable cam 24 in the hatchway should be so adjusted that the roller 54 will strike the cam 24 when the car approaches the terminal at an excessive rate of speed, or a speed which is not sufficiently reduced from normal running speed. As the speed of the car is reduced, the governor 16 lowers the cam 24 which is thereby retracted from the path of the roller 54.

In order that the safety device may become effective to retard the car, in the event that it overruns its normal limits of travel, each guide rail is provided with an enlarged portion 58 adjacent to the bottom of the hatchway, as is clearly shown in Fig. 2, which is a sectional view of the guide rail 34 taken on line 11-11 of Fig. 3.

My invention is best understood, however, when considered with reference to an assumed operation thereof. Assuming that the car is traveling down the hatchway at a normal rate of speed, the governor rope 11 will drive the sheave 12 and the governor 16 at corresponding speeds. If, for some reason, the speed of the car becomes excessive, the governor will turn the ropegripping jaws 17 and 18 to rope-gripping position, and further movement of the governor rope 11 will be prevented. The continued downward movement of the car will then pull the minnie ball 14 from the spring clip 15 and unreel the safety cable 27 from the safety drum 31.

The rotation of the drum 31, resulting from unreeling the cable 27, will force the threaded shafts 38 and. 43 away from each other. As the shaft 38 moves outward, it projects the wedge actuator member 36 between the adjacent extremities of the jaws 32.

As the threaded shaft 43 moves, it carries the cylinder 42 outward, and the fluid therein exerts a pressure on the piston 41 which forces the shaft 39 and the wedge 37 outward. The outward movement of the wedges 36 and 37 carries them between the inner extremities of the rail-gripping jaws 32 and 33 which forces the outer extremities of the jaws toward the guide rails.

As the outer extremities of the jaws approach the rails 34 and 35, their slidably mounted railengaging shoes 51 will be forced into engaging relation therewith, and the downward movement of the elevator car will immediately become effective to move the shoes upwardly relative to the jaws 32 and 33. As the slidably mounted shoe pieces 51 move upwardly, the coaction of the wedge-like formation of these pieces and the inclined backing surfaces presented by the jaws, causes them to be forced against the rails with great pressure. This occurs quickly and causes the maximum braking force to be applied to the rails to retard the car more rapidly than if it depended entirely upon the rotation of the drum 31 by the unreeling of the safety cable 27.

When the rate of retardation of the car exceeds a predetermined rate, the inertia or momentum of the weight 47 tilts the pivoted lever 46, thereby opening the valve 44. As soon as the valve 44 opens, the pressure of the fluid within the cylinder 42 is reduced, thereby diminishing the force applied to the wedges 36 and 37 and the rail- 1 gripping jaws 32 and 33. When the rate of deceleration has been reduced to the maximum allowable rate, the valve 44 will close again.

Hence the rate of deceleration of the car is automatically maintained constant at the predetermined allowable maximum rate. If the rate of deceleration again increases for any reason, such as irregularities in the rails or further relative movement of the pieces 51 in the jaws,

the valve 44 will again open to reduce the pres- 1 ,determined maximum value.

device by unreeling the safety cable 27 from'the drum 31, in the manner set forth above. As the car approaches the terminal, the operator must reduce the speed in order to have the car under control at all times. If he approaches the terminal floor at full speed, he cannot stop the car when it arrives at the floor, and it will, consequently, overrun its normal limits of travel.

During the operation of the car at normal speed, the governor 16 holds the cam 24 up, whereby the links 25 and 26 project it outward into the path of the roller 54. But the cam 24 is so positioned in the hatchway that the roller 54 on the car must pass the cam before the car arrives at its terminal. If the operator reduces the speed in the normal manner, as the car approaches the terminal, the governor will lower the cam 24 which will then be retracted to permit the free passage of the roller 54, and the car may proceed to the terminal at slow speed.

Assuming, however, that the operator does not reduce the speed of the car or does not sufficiently reduce its speed as it approaches the terminal, the roller 54 will engage the cam 24. The cam i 24 will depress the roller 54 to cause the pivoted lever 53 to rotate clockwise, thereby pulling up the rope and lifting the slidable rail-engaging pieces 51 into contact with the guide rails. As the pieces 51 move relatively upward, their tapered formation and the inclined backing surfaces presented by the jaws, cause them to be forced toward the rails. After the initial contact with the rails, the continued downward motion of the car causes the shoe pieces 51 to be forced i against the rails with still greater force, thereby 1 I'ltermined limit, the inertia of the weight 47 causes it to tilt the pivoted lever 46, thereby opening the valve 44 and reducing the pressure of the fluid in the cylinder. The wedge members 36 and 37 may then recede somewhat from their normal position, thereby permitting the jaws 32 and 33 to open somewhat wider than usual to diminish the braking pressure on the rails. As soon as the rate of deceleration of the car has been reduced to the predetermined allowable maximum, the valve 44 will close again whereby a quick smooth stop will be made.

Another mode of operation of my safety system is that which occurs in the event that an elevator car overruns its normal limits of travel at any 1 speed. Assuming that car C runs beyond the discussed.

It will be seen, therefore, that I have provided a safety device which, when actuated, applies the maximum allowable retarding force promptly and thereafter maintains it constant at the pre- As set forth, my system will apply the safety device to stop the car in response to overspeeding in the hatchway, approaching the terminal at an insufficiently reduced rate of speed or overrunning the normal limits of travel at any speed.

Although I have shown and described a specific embodiment of my invention, I am fully aware that many modifications thereof are possible. My invention therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. In combination with an elevator car, a safety device for retarding the car, means for actuating the safety device in response to overspeeding of the car, means for actuating the safety device when the car approaches a terminal at a speed which is in excess of a predetermined safe rate, means for actuating the safety device when the car overruns a terminal, irrespective of speed, and means for reducing the pressure applied by the safety device when the deceleration of the car exceeds a predetermined rate.

1 2. In combination with an elevator car, a safety device for retarding the car, means for actuatng said safety device including fluid-pressure means for transmitting the actuating force, and means responsive to deceleration of the car at a predetermined rate for reducing the effect of the safety device, said means comprising a weight-released valve for reduc'ng the fluid pressure.

3. In combination with an elevator car operating between guide rails, a safety device carried by the car comprising rail-gripping jaws having relatively slidable ral-gripping shoes, means for moving said jaws to rail-gripping position when the car overspeeds at intermediate positions in the hatchway, and means for moving the slidable rail-gripp'ng shoes to rail-gripping position if the speed of the car is not sufficiently reduced below normal as the car approaches a terminal.

4. In combination with an elevator car operating between guide rails, a safety device carried by the car comprising ra l-gripping jaws, rail-engaging shoes, means for moving said jaws to rail-gripping position when the car overspeeds at intermediate positions in the hatchway, means for moving the rail-engag ng shoes to rail-gripping position if the speed of the car is not sufficiently reduced below normal as the car approaches a terminal, and additional means for causing the slidable rail-engaging shoes to engage the rails and retard the car if it overruns the terminal floor, irrespective of speed.

5. In combination with an elevator car operating between guide rails, a safety device carried by the car comprising rail-gripping jaws having relatively slidable rail-gripp ng shoes, means for moving said jaws to rail-gripping position when the car overspeeds at intermediate positions in the hatchway, means for moving the slidable rail-gripping shoes to rail-gripping position if the speed of the car is not sufficiently reduced below normal as the car approaches a terminal, additional means for causing the slidable rail-engaging shoes to engage the rails and retard the car if it overruns the terminal floor, irrespective of its speed, and means for automatically reducing the pressure applied to said safety jaws when the deceleration of the car exceeds a certain rate.

6. In combination with an elevator car operable between guide rails, a safety device carried by the car comprising rail-gripp ng jaws, a relatively movable rail-engaging shoe of tapered form mounted on each jaw in opposing relation to inclined bearing surfaces so that the downward movement of the car is effective to move it into closer engagement with the rail after it has been initially moved into engagement therewith, and means for automatically limiting the rate of retardation applied to the car by the safety device.

7. In combination with an elevator car operable between guide rails, a safety device carried by the car comprising rail-gripping jaws, railengaging shoes, means for supporting one of said shoes on each jaw so that the downward movement of the is effective to move it into closer engagement with the rail after it has been initially moved into engagement therewith, and means responsive to over-speeding of the car for moving said jaws to rail-gripping position.

8. In combination with an elevator car operable between guide rails, a safety device carried by the car comprising rail-gripping jaws, a relatively movable rail-engaging shoe mounted on each jaw, each said shoe and jaw being so formed that the downward movement of the car is effective to move the shoe into closer engagement with the rail after it has been initially moved into engagement therewith, a projectable cam mounted adjacent to the terminal for projection into the hatchway in accordance with the speed of the car, and an actuator member projecting from the car for engagement with said cam to move the relatively movable rail-engaging shoes to rail-engaging position when the car approaches a terminal at a rate of speed which is in excess of a predetermined safe rate.

9. In combination with an elevator car operable between guide rails, a safety device carried by the car comprising rail-gripping jaws, a slidable rail-engaging shoe mounted on each jaw on bearing means which renders the downward movement of the car effective to move it into closer engagement with the rail after it has been initially moved into engagement therewith, and means for moving said slidable rail-engaging shoe to engage the rails when the car approaches the terminal at an excessive rate of speed.

10. In combination with an elevator car operable between guide rails, a safety device carried by the car comprising rail-gripping jaws, a slidable rail-engaging shoe mounted on each jaw on bearing means which renders the downward movement of the car effective to move it into closer engagement with the rail after it has been initially moved into engagement therewith, a pro- "jectable cam mounted adjacent to the terminal for projection into the hatchway in accordance with the speed of the car, an actuator member projecting from the car for engagement with said cam to move the relatively movable rail-engaging shoes to rail-engaging position when the car approaches a terminal at an excessive rate of speed, and means for causing the movable rail-engaging shoe to engage the rails when the car overruns the terminal, irrespective of its rate of speed.

11. In combination with an elevator car operable between guide rails, a safety device carried by the car comprising rail-gripping jaws, a relatively movable rail-engaging shoe carried on each jaw and cooperative means thereon that renders the downward movement of the car effective to move the shoe into closer engagement with the rail after it has been initially moved into engagement therewith, means for moving said movable rail-engaging shoes to engage the rails when the car approaches the terminal at an excessive rate of speed, and an enlarged portion on each guide rail for engaging the jaws to retard the car when it overruns the terminal.

12. In combination with an elevator car operable between guide rails, a safety device carried by the car comprising rail-gripping jaws, railengaging shoes, and means for mounting one of said shoes so disposed on each jaw so that the downward movement of the car is effective to move the shoe into closer engagement with the rail after it has been initially moved into engagement therewith, means for moving the jaws to rail-engaging position when the car overspeeds, and means for automatically reducing the pressure on the jaws when the deceleration of the car exceeds a predetermined rate.

13. In combination with an elevator car operable between guide rails, a safety device for retarding the car comprising rail-gripping jaws, an enlarged portion on each guide rail for engaging the jaws to retard the car when it overruns the terminal, and self-releasing means on said railgripping jaws whereby the rail may be released by starting the car in the reverse direction after said enlarged portion has been engaged.

14. A safety-device for elevator cars operating between guide rails comprising rail-gripping jaws, actuator means for moving the jaws to rail-gripping position, a fluid-pressure device for transmitting the actuating force, and an inertia-controlled valve for regulating the pressure applied in accordance with the rate of retardation resulting therefrom.

15. A safety-device for elevator cars operating between guide rails comprising rail-gripping jaws, rail-engaging shoes, means for mounting one of said shoes on each of said jaws so that the movement of the car is effective to move it into closer engagement with the rail after it has been moved into initial engagement therewith, actuator means for moving the jaws to rail-gripping position in cluding a fluid-pressure device for transmitting the actuating force, and an inertia-controlled valve for regulating the applied actuating pressure in accordance with the rate of retardation resulting therefrom.

JAMES DUNLOP. 

